The invention relates to photographic lenses or objectives of long focal length, and particularly to a system for focusing such lenses.
In order to be able to use long focal length lenses conveniently and reliably, it is known in the art to connect the lens proper or lens mounting parts to the camera by means of an intermediate supporting tube, and to provide the tube with a convenient hand hold or manual gripping part and with a shoulder rest similar to a rifle stock. The manual grip is sometimes developed in two parts arranged so that the pressing of the two parts together by the hand which embraces them effects the focusing motion of a displaceable member in the intermediate tube, the motion of this member serving to carry out the focusing of the lens. Such focusing systems are disclosed, for instance, in West German published patent applications (Offenlegungsschriften) Nos. OS 22 36 344 and OS 22 29 444.
So-called rapid shooting objectives provided with such grips can be used advantageously to photograph moving objects. However, they do not permit precise focusing, and therefore are not suitable for many uses in which an exact focus is necessary, for instance, in order to obtain the highest possible resolution. For such uses, the intermediate tube with the focus setting grip can be replaced with some other mechanism, e.g., a bellows unit, but in order to make the replacement it is necessary to detach the camera and the lens from each other, which is not only inconvenient but also increases the danger of dirt reaching the optical parts of the camera or lens or both.